Disinfecting compositions are frequently used in conjunction with the use of contact lenses to keep lenses clean and free from contaminants including potentially harmful bacteria and fungi. A variety of disinfecting compositions for contact lenses are known. Hydrogen peroxide systems, in particular, 3% hydrogen peroxide, are in common use. Hydrogen peroxide is strongly biocidal and also is a strong oxidizing agent which positively impacts cleaning. However, hydrogen peroxide at the 3% level is also toxic to the eye, and therefore the high levels of hydrogen peroxide used to achieve disinfection must be decomposed to water and oxygen before the lens is safe to reinsert into the eye. This process is known as neutralization or inactivation. Typically, contact lens disinfection systems employ either an enzymic catalyst such as catalase or a metal-based catalyst such as platinum to effect neutralization. A typical disinfection process involves placing a contact lens into a hydrogen-peroxide containing disinfecting solution for a certain period of time, thereby achieving disinfection, followed by a neutralization period whereby the hydrogen peroxide is decomposed, typically by employing a catalytic agent.
Various additional agents may be added to the peroxide solutions to improve cleaning and/or disinfection. For example, surface-active agents may enhance the cleaning or disinfecting properties of the solution. However, these types of agents may also lead to excessive foaming as gas is released during neutralization.
To help ensure that the disinfection is adequate, rubbing and rinsing steps are also frequently recommended. However, these are additional steps that some consumers may not always perform consistently, and so there has been an ongoing effort to design disinfecting systems that do not require the user to perform additional steps such as rubbing or rinsing.
Contact lenses may be broadly divided into two categories, rigid gas-permeable lenses, and soft, hydrogel lenses, although hybrids and other types of lenses exist. Soft or hydrogel lenses have become popular in part because they are comfortable to wear and do not require a period of adaptation. Hydrogels are water swollen three-dimensional polymeric networks that are used in a variety of biomedical applications including drug delivery agents, prosthetic devices and contact lenses. It is well established that the surface characteristics of hydrogels are determined by the orientation of hydrophobic and hydrophilic moieties of the macromolecules. See, e.g., Ketelson et al., Colloids and Surfaces B: Biointerfaces, Vol. 40, pages 1-9 (2005).
Because contact lenses are in intimate contact with the corneal surface and the human tear film, which is composed mainly of proteins, lipids, inorganic cations (e.g., calcium) and mucin, the biocompatibility characteristics of the lenses are directly affected by the surface wettability properties of the hydrogel materials, from which the lenses are formed. In particular, evaluating the surface wettability properties of a lens material is important because such properties affect the stability of the tear film. To maintain a stable tear film, a contact lens material must have hydrophilic surface properties. If the contact lens material becomes hydrophobic, the tear film may be disrupted. To determine the wettability of a surface via an aqueous solution, such as human lacrimal fluid, i.e., tears, the contact angle is measured. The spreading of an aqueous fluid on a surface indicates that the surface is hydrophilic, thereby resulting in a low contact angle. The surface is hydrophobic if a drop of aqueous fluid does not spread, thereby resulting in a high contact angle.
A new family of contact lens materials, silicone hydrogels (“SiH”), is gradually replacing traditional hydrogels as the material of choice for extended wear soft contact lenses. Silicone hydrogel materials have significantly higher oxygen permeability than traditional soft lens hydrogels due to the presence of siloxane functional groups. Additionally, the presence of siloxane groups in SiH materials results in a lens surface having hydrophobic properties. An example of a SiH lens is the Acuvue Advance® contact lenses marketed by Johnson & Johnson.
Various techniques, for example, plasma surface treatments and incorporation of molecules within the lens material, have been utilized in order to provide a biocompatible, hydrophilic and wettable lens surface. Although modifying the surface can improve biocompatibility, it has also been reported that some silicone hydrogel materials accumulate lipids over time, and that this build-up may result in a decrease in the wettability of the silicone hydrogel lens material and surface.
The wettability characteristics of the surfaces of contact lenses may also be modified by reducing the amount of hydrophobization on the surfaces. Surfactants have been utilized in prior compositions for treating contact lenses, for example poloxamers and poloxamines, such as the Pluronic® and Tetronic® brands of surfactants, which are poly(oxyethylene)-poly(oxypropylene) (“PEO-PPO”) block copolymers, have been used extensively in prior products utilized to treat contact lenses. However, such surfactants do not wet SiH lenses efficiently.
U.S. Pat. No. 5,423,012 (Winterton et al.) discloses buffered peroxide formulations with poloxamine or poloxamer surface active agents.
U.S. Pat. No. 5,746,972 (Park et al.) discloses compositions containing hydrogen peroxide and a solid ethylene oxide/propylene oxide block copolymer surfactant having at least 70% by weight polyethylene oxide.
U.S. Pat. No. 7,022,654 (Tsao) discloses compositions containing hydrogen peroxide and hydrophobe-hydrophile block copolymers where the hydrophile component constitutes less than 50 weight percent of the block copolymer.
A new class of surface-active agents has been found to efficiently wet SiH lenses, namely, EO-BO copolymers. However, it has been found that EO-BO copolymers may cause excessive foaming when used in peroxide-based disinfecting solutions during neutralization, for example, with platinum catalyst discs.
U.S. Patent Application Publication No. 2008/0138310 (Ketelson et al.) discloses the use of poly(oxyethylene)-poly(oxybutylene) block copolymers in pharmaceutical compositions.
In view of the foregoing, there is a need for new methods and compositions for improving the wettability of (SiH) contact lenses as well as older lens types while minimizing foaming of peroxide-based contact lens disinfection formulations.